The incidence of prostate cancer (PC) is increasing steadily with the aging population in Singapore. As the pattern of chromosomal aberrations in Asian men with PC is poorly understood, we investigated the numerical aberrations for chromosomes 7, 8, 11, and 17 by fluorescence in situ hybridization (FISH). FISH was performed on standard sections and tissue microarrays of 54 PC and 33 benign prostatic hyperplasia (BPH) specimens. Among the 54 PC specimens, FISH detected 44 cases as aneusomy and two as disomy and was unsuccessful for eight cases. Cytogenetic alterations of two or more chromosomes per tumor were detected in 33/46 (72%) PCs. The most frequent alteration was aneusomy of chromosome 8 detected in 34/46 (74%) cases followed by numerical aberrations in chromosome 7 (61%). Gain of 8q24, loss of chromosome 7, and gain of 11q13 were associated with higher Gleason score and were statistically significant. Gain of chromosome 7 was more common in locally advanced disease, while gain of chromosome 11q13 and chromosome 7 was more common in metastatic disease.